# declare == typeset

# declare -r only-read type value
declare -r var="hello"
var="world"

# declare -i int value
num1=2001
declare -i num2
num2=$num1+1
echo $num2

# declare -a
declare -a array=("jones" "mike" "kobe" "jordan")
# show all item
echo ${array[@]}
# show index 1 item
echo ${array[1]}
# show array length
echo ${#array}
# show index 1 item length
echo ${#array[1]}

# declare -x enviroment value
